Title

Author

Date of Award

2013

Document Type

Thesis

Degree Name

Master of Science (MS) in Biology

Department

Biology

First Advisor

Allan Scholz

Second Advisor

A. Ross Black

Third Advisor

Doris Munson

Abstract

This study determined which kokanee stock performed best in Lake Roosevelt, WA: Lake Whatcom, Meadow Creek, or F1 mixed stock. The F1 mixed stock was created by collecting eggs from Lake Whatcom, Meadow Creek and non-marked kokanee that returned to Hawk Creek and raising them to the residualized smolt stage at the Spokane Tribal hatchery for release back into Lake Roosevelt. Fall spawning run data (2009 – 2012) were analyzed to assess the percentage and sex ratios of each stock returning to spawn in Lake Roosevelt. We had record returns of hatchery kokanee in 2009 (n = 8,895) and 2010 (n = 8,925), but poor returns in 2011 (n = 423) and 2012 (n = 1,893). The F1 mixed stock significantly outperformed the Lake Whatcom and Meadow Creek stocks for both return percentage (P <0.001) and sex ratios (P <0.001) in each year. The record kokanee returns of 2009 and 2010 coincided with relatively shallow drawdown and longer water retention times, whereas, the poor 2011 and 2012 returns coincided with a deep drawdown and shorter water retention times.